K 3-35 : planetary nebula or compact HII region ?

The authors have detected OH and H₂O maser emission from the suspected planetary nebula K3-35. The OH masers are found to have Type II characteristics with emission at 1612 MHz stronger than at 1667 MHz and with no detectable emission at 1665 MHz. The H₂O maser is at a velocity outside the range of the 1612 MHz emission. Measurements at the CO(J = 1→0) frequency show extended emission at a velocity close to that of the strongest OH maser lines. The authors find it possible that K3-35 was misclassified and is rather a compact H II region associated with the molecular cloud L 755.